Improvement in wood-soeews



@ni-ten tetra attent ffice.

JASON A. BIDWELL, OF EAST BOSTON, MASSACHUSETTS.

Letters .Patent No. 74,489, dated .February I8, 1868.

IMPROVEMENT IN WOOD-SGRBWS.

TO ALL WHOM IT MAY CONGERN:

Be it known that I,'JAsoN.A. BIDWELL, of East Boston, Su'olk county, Stato of Massachusetts, have invented an Improved Wood-Screw; and I do hereby declare the following to be a full, clear, and exact descrip. tion thereof, reference being had to the accompanying drawings, making part of this specification, in which- Figure 1 is a side view of the improved screwt Figure 2 is a diametrical section through the screw.

Figure 3 is an end view. 4 V

Figure 4 is an enlarged sectional view of a portion `of the screw, showingy clearly the form of the thread.

Similar letters of reference indicate corresponding parts in the several gnres.

The object of this invention is to construct a wood-screw which will penetrate wood more readily, and have a firmer hold than wood-screws hitherto made. v

The nature of my invention consists in a. wood-screw having a core, which tapers from the shanl: to the point, and a thread which does not taper, except at the entering-point ofthe screw, said thread being constructed with double convex sides, so as to increase the bearing-surface, and'add g'rcater strength to it, as will be hereinafter described. i V

vTo enable others skilled in the art to understand my invention, I will describe its construction and operation.

In the accompanying drawings,a represents the head of the scre\\,'\vhich may be notched or slotted, as

shown, or it may be perforated; and b represents the cylindrical shank or neck of the screw, which extends from the head to the point, c, where the screw-thread commences. The thread commences at'the.,circunnfer` V ence of the shank b, and gradui'ally increases `in depth, until the full depth ofthe screw isohtained, thereby producing the conical core e, which maybe more or less tapering, as desired. The core g, upon which the full thread d is formed, commences at the termination of the conc-shoulder e, and continues to the entering-pointf, with a gradual taper, as shownin gs. 1 and 2. The'thr'ead d cl is of the same diameter as ,the shank b, from the point c to the point t, when it is gradually reduced, so as to form the ventering-point. It will be seen that the portion d of the thread of my screw abruptly increases in depth upon the conical shoulder e', and then gradually increases in depth from this point to the reduced' entering-cud. Instead of'maliing the surfaces of the thread at, as in some wood-screws hitherto, vI make these surfaces convex or rounding, as shown in figs. 2 and 4, so as to increase their thickness, and consequently increase the strength ofthe thread. The case of the thread also increases in thickness as it approaches the entering-point of the screw, so that it shall not have its strength diminished as it is increased in depth.A V

It will be seen from the above description and :iccompanying drawings, that no part of the core of inv4 improved screw is cylindrical, but that it forms a conical wedge, whichwill enter wood without driving the fibres in advance of it. The fibres of the wood will'be spread out laterally, and compacted between and outside of the thread, while the latter will wind its way down into the wood, andseeue n. firm `h olcl therein.

Having described my invention, what I claim as new, and desire to secure by Letters Patent, 'is- As a new and improved article of manufacture, a wood-screw, having' its core tapering from its shank toits.'

entering-point, and provided with a thread of uniform diameter, as herein described.

JASON A. BIDWELL.

Witnesses:

.WiL B. W. HALLETT,

STEPHEN A. COOKE, Jr. 

